Switchable imaging apparatus for viewing and capture

ABSTRACT

A switchable imaging apparatus having a transparent viewing mode and an image capture mode, comprising: a transparent plate having a front surface, wherein a scene is viewable through the transparent plate when the imaging apparatus is in the transparent viewing mode; an optical beam deflector positioned within the transparent plate, wherein the optical beam deflector is switchable between a first non-deflecting state and a second deflecting state, such that when the optical beam deflector is in the second deflecting state imaging light from the scene is deflected into a camera positioned in a location peripheral to the transparent plate; and a controller which synchronously switches the optical beam deflector between the first non-deflecting state and the second deflecting state, thereby providing the transparent viewing mode and the image capture mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly assigned, co-pending U.S. patentapplication Ser. No. ______/______ (docket K000012), entitled:“Switchable imaging apparatus for display and capture”, by Border etal.; to commonly assigned, co-pending U.S. patent application Ser. No.______/______ (docket K000318), entitled: “Imaging apparatus withswitchable beam deflector array”, by Manico et al.; to commonlyassigned, co-pending U.S. patent application Ser. No. ______/______(docket K000319), entitled: “Imaging apparatus with dual switchable beamdeflectors”, by Border et al.; and to commonly assigned, co-pending U.S.patent application Ser. No. ______/______ (docket K000320), entitled:“Capturing images using a switchable imaging apparatus”, by Border etal., each of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention pertains to the field of image capture and moreparticularly to a device that uses a switchable beam deflector toprovide a transparent viewing mode and an image capture mode.

BACKGROUND OF THE INVENTION

Devices that integrate the functions of both display and image capturehave been proposed for use in videoconferencing and other functions, asdescribed in commonly assigned U.S. Pat. No. 7,714,923 entitled“Integrated display and capture apparatus” to Cok et al. In suchdevices, the camera components used for image capture are integrallyformed to share space with display components on the surface of the samescreen. This advantageous arrangement helps to allow a more naturalinteraction between viewers positioned at their respective displays. Theterm “displays that see (DTS)” has been coined to describe a class ofsuch devices.

Increased demand for more compact device packaging presents a particularchallenge for DTS designs. To provide a handheld device of this type,such as a camera with a display visible to the subject, it is necessaryto reduce device dimensions and weight as much as possible, withoutcompromising its display or image capture functions.

With conventional optical solutions for camera optics, there aretrade-offs between size and thickness of the DTS device and imagequality. The optical path length can be severely constrained, increasingoptical design complexity and cost. Placing one or more cameras behindthe display screen can add significant thickness and bulk and may beimpractical for a hand-held device. Positioning one or more camerasalong edges of the display screen may alleviate some of the dimensionalproblems, but proves to be less satisfactory because the perspective ofthe camera is different from the perspective of a viewer who isobserving the display.

In transparent displays, cameras in the display area obstruct thetransparency of the display. While displays such as active matrix OLEDs(AMOLED) can be highly transparent, camera components such as an imagesensor are typically opaque. What is needed is a method to capture animage from the perspective of the center of the display while locatingthe opaque components of the camera at the edge of the display. In thepaper “Liquid Crystal Based Optical Switches” by Semenova et al (Journalof Molecular Crystals and Liquid Crystals, Vol. 413, pp. 385-398, 2004),optical switches are provided that redirect light when activated.However, the optical switches described are dependent on the light beingpolarized and prisms are used to increase the angular redirection of theoptical switch. As such, the optical switches described are not suitedfor use in a transparent display because the light interacting with thedisplay is not polarized and prisms would distort the transparent viewthrough the transparent display.

U.S. Pat. No. 4,385,799 to Soref, entitled “Dual array fiber liquidcrystal optical switches,” presents an optical switch fortelecommunications that is based on liquid crystals. In this case, areflection from a liquid crystal layer is used to interrupt a beam oflight. As such, a small deflection of the beam of light is sufficient tointerrupt the beam and switch OFF the telecommunication. The deflectionprovided by this optical switch, however, is slight, and is too small tobe used in a transparent display.

U.S. Pat. No. 5,018,835 to Dorschner, entitled “Deflector for an opticalbeam including refractive means,” provides a deflector for an opticalbeam based on a liquid crystal layer. In this patent, a prism element iscombined with a series of stripe electrodes to deflect an optical beamby different amounts. U.S. Pat. No. 6,999,649 to Chen, entitled “Opticalswitches made by nematic liquid crystal switchable mirrors, andapparatus of manufacture,” provides a similar deflector which includes aprism element to increase the angle of deflection. Since thesedeflectors utilize prism elements, they would provide distorted viewsthrough transparent displays. U.S. Pat. No. 6,687,030 to Popovich etal., entitled “Method and apparatus for illuminating a display,”discloses an image generating apparatus including a switchablelight-directing apparatus. In response to a control signal, theswitchable light-directing apparatus directs portions of received lightonto different regions of an image plane. U.S. Pat. No. 6,885,414 to Li,entitled “Optical router switch array and method for manufacture,”discloses an optical router switch array including a plurality ofindividually switchable mirror elements. The switchable mirror elementsare made using liquid crystal holographic gratings.

Although various configurations have been proposed for providing a DTSdesign, conventional solutions fall short of a solution that reduces thephysical profile of the device, provides alignment between theperspective of the camera and the perspective of the display as observedby a viewer, and conceals or masks image capture components fromvisibility to the viewer who is also being imaged. Thus, it is seen thatthere is a need for an improved DTS design that addresses thesedifficulties.

SUMMARY OF THE INVENTION

The present invention represents a switchable imaging apparatus having atransparent viewing mode for viewing a scene and an image capture modefor capturing an image of the scene, comprising:

a transparent plate having a front surface, wherein the scene isviewable through the transparent plate when the imaging apparatus is inthe transparent viewing mode;

an optical beam deflector positioned within the transparent plate, or inproximity to the transparent plate, wherein the optical beam deflectoris switchable between a first non-deflecting state and a seconddeflecting state, such that when the optical beam deflector is in thefirst non-deflecting state, light from the scene passes through theoptical beam deflector in an undeflected direction, and when the opticalbeam deflector is in the second deflecting state, light from the sceneis deflected from a first optical axis perpendicular to the frontsurface of the transparent plate onto a second optical axis parallel tothe front surface of the transparent plate;

a camera positioned along the second optical axis in a locationperipheral to the transparent plate; and

a controller which synchronously switches the optical beam deflectorbetween the first non-deflecting state and the second deflecting stateand initiates capture of an image by the camera, thereby providing thetransparent viewing mode and the image capture mode.

This invention has the advantage that an image capture device isprovided that can be switched between a transparent viewing mode and animage capture mode such that the camera components used to capture animage of the scene are invisible to both the photographer and thesubject while the image is being composed.

It has the additional advantage that the device has the appearance of atransparent window. This allows the person taking the image to use thewindow itself as the “viewfinder” for a more natural image capturesession.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of the Total Internal Reflection (TIR)principle that is used for a switchable beam deflector in accordancewith the present invention;

FIG. 2A shows a cross-sectional view of a switchable beam deflectoroperating in a non-deflecting state;

FIG. 2B shows a cross-sectional view of a switchable beam deflector in adeflecting state;

FIG. 3A shows a cross-sectional view of a transparent plateincorporating a switchable beam deflector;

FIG. 3B shows a cross-sectional view of a switchable imaging apparatus;

FIG. 4 illustrates a configuration for using the switchable imagingapparatus of FIG. 3B;

FIG. 5A shows a cross sectional view of a switchable imaging apparatusoperating in an image display mode;

FIG. 5B shows a cross sectional view of the switchable imaging apparatusof FIG. 5A operating in an image capture mode;

FIG. 6A illustrates a first configuration for using the switchableimaging apparatus of FIG. 6B in a photography application;

FIG. 6B illustrates a second configuration for using the switchableimaging apparatus of FIG. 6B in a photography application;

FIG. 6C illustrates a third configuration for using the switchableimaging apparatus of FIG. 6B in a photography;

FIG. 6D illustrates a fourth configuration for using the switchableimaging apparatus of FIG. 6B in a teleconference application;

FIG. 7A shows a cross sectional view of a switchable imaging apparatusoperating in an image display mode according to an alternate embodiment;

FIG. 7B shows a cross sectional view of the switchable imaging apparatusof FIG. 7A operating in an image capture mode;

FIG. 8A shows a cross sectional view of a switchable imaging apparatusoperating in an image display mode according to an alternate embodimentusing an array of individually switchable beam deflectors;

FIG. 8B shows a cross sectional view of the switchable imaging apparatusof FIG. 8A operating in an image capture mode;

FIG. 9 illustrates a configuration for using the switchable imagingapparatus of FIGS. 8A and 8B;

FIG. 10 shows a cross sectional view of a switchable imaging apparatusaccording to an alternate embodiment incorporating a pair of switchablebeam deflectors oriented in opposite directions;

FIG. 11 shows a cross sectional view of a switchable imaging apparatusaccording to an alternate embodiment incorporating a pair of switchablebeam deflectors oriented in opposite directions and a pair of displayscreens; and

FIG. 12 illustrates a configuration for using a switchable imagingapparatus in accordance with the present invention.

It is to be understood that the attached drawings are for purposes ofillustrating the concepts of the invention and may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

The invention is inclusive of combinations of the embodiments describedherein. References to “a particular embodiment” and the like refer tofeatures that are present in at least one embodiment of the invention.Separate references to “an embodiment” or “particular embodiments” orthe like do not necessarily refer to the same embodiment or embodiments;however, such embodiments are not mutually exclusive, unless soindicated or as are readily apparent to one of skill in the art. The useof singular or plural in referring to the “method” or “methods” and thelike is not limiting. It should be noted that, unless otherwiseexplicitly noted or required by context, the word “or” is used in thisdisclosure in a non-exclusive sense.

Embodiments of the present invention utilize one or more switchablelayers of transparent material that change from a low refractive indexstate to a high refractive index state when exposed to anelectromagnetic field. The switchable layers of transparent material arepositioned inside a substrate of transparent material to form aswitchable optical beam deflector. The materials are chosen so that thesubstrate material has substantially the same refractive index as theswitchable layers of transparent material when they are in their highrefractive index state. As a result, the switchable beam deflector issubstantially transparent when the switchable layers of transparentmaterial are in their high refractive index state, since the substratematerials have the same refractive index. Conversely, when theswitchable layers of transparent material are in their low refractiveindex state, the refractive indices of the substrate materials are notthe same and the switchable beam deflector is not fully transparent, assome of the light passing through the plate will be reflected by totalinternal reflection (TIR).

TIR occurs when a ray of light, traveling through a material with afirst refractive index n₁ , is incident on a surface of another materialhaving a lower second refractive index n₂, and the incident angle of theray of light is at or above a critical angle θ_(c), with respect to anormal to the surface. The critical angle θ_(c) is defined in Eq. (1)below:

θ_(c)=sin⁻¹(n ₂ /n ₁)   (1)

FIG. 1 shows the TIR principle in schematic form for light travelingfrom a first material 60 having a first refractive index n₁ and incidenton a second material 62 having a lower second refractive index n₂. Atangles less than the critical angle (θ<θ_(c)), the light travels throughthe interface 64 between first and second materials 60 and 62, with someredirection due to refraction, as shown. At angles greater than or equalto the critical angle (θ≧θ_(c)), the light is fully reflected at theinterface by TIR. TIR is used, for example, in optical fibers and inother optical applications, because it is highly efficient, reflectingsubstantially all of the incident light under the given conditions.

A number of materials are capable of being switched between differentrefraction indices in response to an applied electromagnetic signal. Inparticular, various types of liquid crystal materials are known toexhibit measurable changes in optical refractive index for only modestchanges in an applied electric field. This principle has been describedfor use in various types of electro-optical switches, such as thosedescribed in U.S. Pat. No. 4,278,327 to McMahon et al., entitled “LiquidCrystal Matrices,” for example. A typical difference in refractiveindex, An, is in the range of about 0.05 to 0.5 for different types ofliquid crystal materials. Consistent with an embodiment of the presentinvention, one or more layers of liquid crystal materials are embeddedwithin a transparent substrate and provided with a switching signal thatenables switching between two refractive indices to provide lightredirection within beam deflector.

FIGS. 2A and 2B are schematic diagrams showing a switchable optical beamdeflector 50 in non-deflecting and deflecting states, respectively,based on electrical signals applied according to instructions from acontroller. A transparent substrate 52 has one or more liquid crystallayers 54 of a liquid crystal material. The liquid crystal layers 54have a switchable refractive index that can be switched in response toan applied voltage signal. In FIG. 2A, application of a first voltagesignal (e.g., V=0) causes a refractive index n_(L) of the liquid crystallayers 54 to closely match a refractive index n_(S) of the substrate 52(or at least to match closely enough so that the critical angleθ_(c)=sin⁻¹(n_(L)/n_(S)) is greater than the angle of incidence θ₁ foran incoming light ray R1.) In this configuration, incoming light, shownalong parallel rays R1 and R2, is transmitted undeflected through theinterface between the liquid crystal layers 54 and the substrate 52. Aswill be described later, this condition can be used to provide a“display state” for a switchable imaging device, wherein the incominglight can be modulated to provide a displayed image.

In FIG. 2B, application of a second voltage signal (e.g., V=V₀) causesthe refractive index n_(L) of the liquid crystal layers 54 to be lowerthan the refractive index n_(S) of the substrate 52. This causes TIR forlight along ray R2, because it is incident on the liquid crystal layer54 at an angle of incidence θ₁ larger than the critical angle θ_(c).Light along ray R1 is not incident on the liquid crystal layer 54 at anangle larger than the critical angle θ_(c), and thus passes through theliquid crystal layer 54 substantially undeflected.

As shown by the redirected path of ray R2 in FIG. 2B, multiple layers54, oriented at different angles, can be used to deflect the incidentlight by a greater amount. In the present invention the incident lighton optical axis O is deflected by 90° to a redirected optical axis O′ sothat incoming light from the scene in front of the device can bedirected to a camera or other type of image sensor, thereby providing a“capture state” for the switchable imaging apparatus.

Examining the path of light ray R2 in FIG. 2B, it can be seen that whenTIR conditions are met, the layers 54 act as mirrors that each providedeflections of twice the angle between the input ray and the interface.As a result, it can be shown that the desired 90° deflection is obtainedprovided that TIR conditions are met with angles of incidence ofθ₁=θ₂=90°−90°/4=67.5°. Thus the critical angle must be θ_(c)≦67.5°.However, it should be noted that since liquid crystal layers aretypically polarization-sensitive, the deflection of the light ray R2will occur only for one of the polarization states present in theincoming light, the light with the other polarization state will not beaffected by the liquid crystal layer 54 and as such will pass throughthe liquid crystal layer 54 similar to light ray R1. In thisconfiguration, the angles of incidence θ₁=θ₂=67.5° are provided when theliquid crystal layers are oriented at θ_(L1)=67.5° and θ_(L2)=22.5°.However, it will be obvious to one skilled in the art that otherarrangements can be used to provide the desired 90° deflection of theincoming light ray.

FIG. 3A is a schematic diagram showing cross-sectional view of atransparent plate 110 incorporating a switchable beam deflector 50 thatcan be used in accordance with various embodiments of the presentinvention. The switchable beam deflector 50 includes two liquid crystallayers 54 similar to those shown in FIGS. 2A and 2B. The transparentplate 110 is made from three transparent plate sections 111 a, 111 b and111 c to simplify construction and allow for transparent electrodes 113a and 113 b to be applied to the opposite sides of thin cavitiesprovided for the liquid crystal layers 54. Preferably, alignment layersare also provided in the thin cavities as is well known by those skilledin the art but are not shown in the drawings. After the transparentplate sections 111 a, 111 b and 111 c have been manufactured and coatedwith transparent electrodes 113 a and 113 b, and the liquid crystallayers 54 are positioned in the thin cavities, the transparent platesections 111 a, 111 b and 111 c are bound together and sealed to encloseand protect the liquid crystal. In some embodiments, sealing can beprovided by thin transparent plates (not shown) that cover the frontside and back side of the transparent plate 110.

FIG. 3B is a schematic diagram showing cross-sectional view of aswitchable imaging apparatus 120 incorporating the transparent plate 110of FIG. 3A according to one embodiment. The switchable imaging apparatus120 has a transparent viewing mode for viewing a scene and an imagecapture mode for capturing an image of the scene. The imaging apparatus120 includes a controller 40 for controlling the switchable beamdeflector 50. The controller 40 is connected to the transparentelectrodes 113 a and 113 b using control wires 44. By controlling thevoltage difference between the transparent electrodes 113 a and 113 b,the controller 40 can control the refractive index of the liquid crystallayers 54, thereby enabling the switchable beam deflector 50 to beswitched between the first non-deflecting state and the seconddeflecting state.

When the switchable beam deflector 50 is controlled to operate in thefirst non-deflecting state, the switchable beam deflector 50 istransparent in order to provide the transparent viewing mode for theswitchable imaging apparatus 120. In this mode, a viewer can view thescene by looking through the transparent plate 110, much as one wouldlook through a glass window.

When the switchable beam deflector 50 is controlled to operate in thesecond deflecting state, light is deflected by TIR from the liquidcrystal layers 54 so that light from a first optical axis Operpendicular to the surface of the transparent plate 110 and extendingfrom the front side of the switchable imaging apparatus 120 is deflectedonto a second optical axis O′ parallel to the surface of the transparentplate 110. The deflected light is directed onto a camera 34, in order toprovide the image capture mode for the switchable imaging apparatus 120.In the context of the present invention, the “front side” of theswitchable imaging apparatus 120 is defined to be the side facing towardthe scene being imaged when the switchable imaging apparatus 120 isbeing operated in the image capture mode. Similarly, the “back side” isdefined to be the opposite side facing away from the scene.

The camera 34 is preferably a digital camera and includes imaging optics32 and an imaging sensor 33, and is configured to capture an image ofthe scene over a field of view 18. The imaging sensor 33 includes anarray of image sensor pixels, and can be any of a number of types ofimage sensing devices that are known in the art. Examples of typicalimage sensing devices that can be used in accordance with the presentinvention include charge-coupled devices (CCD) or complementarymetal-oxide semiconductor (CMOS) devices. The array of image sensorpixels will generally be a two-dimensional array, although in someembodiments a one-dimensional array can be used.

The switchable imaging apparatus 120 will generally include otherelectronic and mechanical components providing various features such asuser interface controls, supply of electrical power, image processingoperations, storage of captured images and connectivity with otherdevices. The transparent plate 110 can be positioned in a variety offrame configurations (not shown). The camera 34, the controller 40 andthe other associated components are preferably built into the frame usedto enclose the transparent plate 110.

FIG. 4 illustrates the use of the switchable imaging apparatus 120 ofFIG. 3B by a photographer 12 to capture an image of a subject 16. As thephotographer 12 prepares to capture the image, the switchable imagingapparatus 120 is controlled to be in the transparent view mode so thatfrom the photographer's view 17, the switchable imaging apparatus 120appears to be a transparent window, through which the subject 16 can beseen. When the photographer 12 has positioned the switchable imagingapparatus 120 properly and is satisfied with the pose of the subject 16,an image capture control such as a “shutter button” (not shown) can beactivated to initiate capture of the image. In response to activation ofthe image capture control, the controller 40 (FIG. 3B) switches theswitchable beam deflector 50 (FIG. 3B) to operate in the deflectingmode, which deflects light from the scene into the camera 34 (FIG. 3B),which then captures the desired image. The switchable beam deflector 50only needs to be switched to the deflecting mode for the fraction of asecond required to capture the image, then it can be returned to thenon-deflecting mode for the transparent viewing state. For video captureapplications, the switchable beam deflector 50 can be alternatelyswitched between the deflecting state for the image capture mode and thenon-deflecting state for the image display mode (or the transparent viewmode) at rates suitable to capture motion video.

FIGS. 5A and 5B are schematic diagrams showing cross-sectional views ofa switchable imaging apparatus 10 according to a second embodiment. Inthis embodiment, the switchable imaging apparatus 10 incorporates adisplay screen 20 positioned between the scene and the optical beamdeflector 50 such that the imaging light passes through the displayscreen 20 before being deflected by the optical beam deflector 50. Thedisplay screen 20 can be switched to provide both an image display mode(as shown in FIG. 5A) and an image capture mode (as shown in FIG. 5B).The switchable imaging apparatus 10 is similar to the imaging device 120from FIG. 3B, except for the addition of the display screen 20 and anoptional light blocking layer 36. In some configurations, the lightblocking layer 36 can be omitted, or a transparent layer can be used inplace of the light blocking layer 36.

The switchable imaging apparatus 10 includes a switchable beam deflector50, such as that described in FIG. 3A. In the illustrated configuration,the transparent plate 110 incorporating the switchable beam deflector 50is sized such that it is only as large as the switchable beam deflector50. The remaining region between the display screen 20 and the lightblocking layer 36 is filled by an air gap 56. In other embodiments, thetransparent plate 110 can extend to fill the entire region between thedisplay screen 20 and the light blocking layer 36.

The display screen 20 includes an array of display pixels energizable toprovide a displayed image when the display screen is in a first displaystate. The display screen 20 should be at least partially transparentwhen the display screen 20 is switched to a second transparent statewhere the display pixels are not energized so that light can bedeflected by the switchable beam deflector 50 into the camera 34. Onetype of display technology that can be at least partially transparent isan Optical Light Emitting Diode (OLED) display, such as that provided inthe Mobile Display from Samsung, Seoul, Korea.

The switchable imaging apparatus 10 will generally include otherelectronic and mechanical components providing various features such asuser interface controls, supply of electrical power, image processingoperations, storage of captured images and connectivity with otherdevices. As with the switchable imaging apparatus 120 described earlier,these components can be built into a variety of frame structure thatsurrounds the display screen 20.

In FIG. 5A, the switchable imaging apparatus 10 is shown operating inthe image display mode. In the image display mode, the controller 40controls the switchable beam deflector 50 to operate in itsnon-deflecting state and the display screen 20 to operate in its displaystate where the display pixels are energized to provide a displayedimage. By controlling the switchable beam deflector 50 to operate in thenon-deflecting state when images are displayed, a higher quality imagecan be displayed without shadows that would be caused if the switchablebeam deflector 50 were switched to the deflecting state.

In some embodiments, the optional light blocking layer 36 is used toprovide a uniform background behind the display. This prevents objectsbehind the switchable imaging apparatus 10 from being visible throughthe displayed image. The light blocking layer 36 can be an opaque lightblocking layer, such as a black layer or a white layer. In otherembodiments, the light blocking layer can be a light scattering layer,such as an optical diffuser.

In some embodiments, the light blocking layer 36 is switchable between alight blocking state or light scattering state and a transparent stateaccording to control signals received from the controller 40. In thisway the switchable imaging apparatus 10 can be controlled to provide anoptional transparent mode where the display screen 20 is controlled tooperate in its transparent state, the switchable beam deflector 50 iscontrolled to operate in its non-deflecting state, and the lightblocking layer 36 is controlled to operate in its transparent state.Methods for making switchable light blocking layers are known in theart. For example, a switchable light blocking layer that switchesbetween a transparent state and a light scattering state can be madeusing the methods provided in U.S. Pat. No. 4,688,900 to Doane et al.,entitled “Light modulating material comprising a liquid crystaldispersion in a plastic matrix.” With this approach, the droplets ofliquid crystal are enclosed in a clear plastic sheet. The material canbe switched between a transparent state and a scattering state byswitching between two different alignments for the birefringent liquidcrystal molecules. Similarly, a switchable light blocking layer thatswitches between a transparent state and a light blocking state can bemade using the methods described in U.S. Pat. No. 3,499,702 toGoldmacher, entitled “Nematic liquid crystal mixtures for use in a lightvalve.” With this approach the polarization state of liquid crystallayers is rotated so that light is alternately controlled to be passedor blocked. Alternately, pleochroic dyes can be combined with liquidcrystal materials to switch between a transparent state and an absorbingstate.

When the display screen 20 is operating in its display state, the lightblocking layer 36 can optionally be switched between its transparentstate and its light blocking/light scattering state according to therequirements of a particular application or according to a specifieduser preference. If the light blocking layer 36 is controlled to operatein its transparent state while the display screen 20 is in its displaystate, the result will be a semi-transparent image display where thebackground is visible through the displayed image. If the light blockinglayer 36 is controlled to operate in its light blocking/light scatteringstate while the display screen 20 is in its display state, thebackground will not be visible through the displayed image.

In FIG. 5B, the switchable imaging apparatus 10 is shown operating inthe image capture mode. In the image capture mode, the controller 40controls the switchable beam deflector 50 to operate in its deflectingstate and the display screen 20 to operate in its transparent state (atleast in the area of display pixels covering the field of view 18 forthe switchable beam deflector 50). In the image capture mode, light isdeflected by the switchable beam deflector so that light from the firstoptical axis O, which is perpendicular to the display screen 20 andextends out of the front side of the display screen, is deflected ontothe second optical axis O′, which is parallel to the display screen 20.The deflected light is directed onto the camera 34, which captures animage of the scene over the field of view 18.

The switchable imaging apparatus 10 shown in FIGS. 5A and 5B can be usedfor a variety of applications. For example, in FIG. 6A the switchableimaging apparatus 10 is used by photographer 12 to capture an image ofsubject 16. In this application, the switchable imaging apparatus 10 isset to operate in the image display mode during the time that thephotographer 12 is composing the image and waiting for the subject 16 tohave an attractive smile. The display screen 20 can be activated todisplay an image 14 to the subject 16 during this process as illustratedby the subject's view 19. For example, the displayed image 14 caninclude a text message giving instructions to the subject 16 (e.g.,“Smile!”). The text message capability can also be used to enable anumber of different applications. For example, the switchable imagingapparatus 10 can be used to present scrolling text for teleprompter orkaraoke applications, while simultaneously capturing video or stillimages of the subject 16. This has the advantage that the subject 16will be looking directly into the camera while he/she is reading thetext.

Alternately, the displayed image 14 can provide a preview image showingthe subject 16 what she looks like so she can adjust her poseappropriately. (This can be particularly convenient for enabling thephotographer 12 to capture a self-portrait by orienting the displayscreen 20 to point toward himself) In order to capture the previewimage, the switchable imaging apparatus 10 can be configured to rapidlyalternate back and forth between the image capture mode and the imagedisplay mode. An image can then be captured with the switchable imagingapparatus 10 is in the image capture mode, and can be displayed on thedisplay screen 20 after the switchable imaging apparatus 10 has switchedback to the image display mode. The captured image is represented by anarray of pixel values, and is displayed by energizing the display pixelsof the display screen 20 in accordance with the pixel values of thecaptured image. If the image capture mode and the image display mode arealternated at a high enough temporal frequency, the subject 16 will notnotice any observable flicker (e.g. 60 Hz).

When the photographer 12 is satisfied with the pose of the subject 16,an image capture control (not shown) can be activated to initiatecapture of the image. In response to activation of the image capturecontrol, the controller 40 (FIG. 5B) switches the switchable imagingapparatus 10 to operate in the image capture mode and captures thedesired image. The switchable imaging apparatus 10 only needs to beswitched to the image capture mode for the fraction a second required tocapture the image, then it can be returned to the image display modewhere the captured image can then be displayed on the display screen 20.

The switchable imaging apparatus 10 can also be used for a wide varietyof other applications. For example, U.S. Pat. No. 7,003,139 toEndrikhovski et al., entitled “Method for using facial expression todetermine affective information in an imaging system,” and U.S. Pat. No.7,233,684 to Fedorovskaya et al., entitled “Imaging method and systemusing affective information,” both of which are incorporated herein byreference, teach that a user's facial expression can be monitored whileviewing an image in order to automatically infer user image preferences.This approach can be used to automatically tag images with metadataindicating the user's positive or negative response to the viewedimages. In this scenario, the images to be viewed can be presented onthe display screen 20 for viewing by the subject 16. The facialexpression of the subject 16 can then be monitored by capturing imagesusing the camera 34 (FIG. 5A). The determined metadata tags can then bedisplayed on the display screen 20 (e.g., as a numeric or textrepresentation, or as a “star rating”).

Similarly, U.S. Pat. No. 7,046,924 to Miller et al., entitled “Methodand computer program product for determining an area of importance in animage using eye monitoring information,” and U.S. Pat. No. 7,206,022 toMiller et al., entitled “Camera system with eye monitoring,” both ofwhich are incorporated herein by reference, teach that eye gaze can bemonitored while a user is viewing an evaluation image to determine whatpart of the image a user is interested in. The switchable imagingapparatus 10 can be used to enable these applications by capturingimages of the subject 16 while he/she is viewing the evaluation imagedisplayed on the display screen 20. The captured images of the subject16 can then be monitored to determine the eye gaze pattern. Once the eyegaze pattern has been determined, this information can be used for avariety of purposes. In some embodiments, the evaluation image can beadjusted in response to the eye gaze pattern. Alternately, the image canbe tagged with metadata indicating regions of interest in the image.

In configurations where the light blocking layer 36 is not included, orwhere the light blocking layer 36 can be switched to a transparent mode,the displayed image 14 can be semi-transparent allowing the photographer12 to view the subject 16 (and likewise for the subject 16 to view thephotographer 12) through the displayed image 14, as illustrated in FIG.6B.

FIG. 6C shows an alternate configuration where the switchable imagingapparatus 10 is controlled to operate in the optional transparent modedescribed early during the time that the photographer 12 is composingthe image. In this case, from the subject's view 19, the subject 16 willbe able to see the photographer 12 through the transparent switchableimaging apparatus 10, and from the photographer's view 17, thephotographer 12 will be able to see the subject 16 through thetransparent switchable imaging apparatus 10.

FIG. 6D shows a third example where the switchable imaging apparatus 10of FIGS. 5A and 5B is used for a teleconferencing application. In thisconfiguration a first person 13 a has a first switchable imagingapparatus 10 a, and a second person 13 b has a second switchable imagingapparatus 10 b. The first switchable imaging apparatus 10 a and thesecond switchable imaging apparatus 10 b include appropriatecommunications components that enable them to communicate with eachother across a communications network 15. The communications network 15can either be a wired network, or a wireless network such as a WIFInetwork or a cell phone communications network.

In this teleconferencing application, the first switchable imagingapparatus 10 a and the second switchable imaging apparatus 10 b are bothset to rapidly alternate back and forth between the image display modeand the image capture mode. While the first switchable imaging apparatus10 a is controlled to operate in its image capture mode, it captures animage of the first person 13 a. This image is then transmitted to thesecond switchable imaging apparatus 10 b where it is displayed on itsdisplay screen as image 14 b when the second switchable imagingapparatus 10 b is controlled to be in its image display mode. Likewise,while the second switchable imaging apparatus 10 b is controlled tooperate in its image capture mode, it captures an image of the secondperson 13 b. This image is then transmitted to the first switchableimaging apparatus 10 a where it is displayed on its display screen asimage 14 a when the first switchable imaging apparatus 10 a iscontrolled to be in its image display mode. Video communication isprovided by capturing and transmitting the images back and forth atperiodic intervals. An audio channel captured at the first switchableimaging apparatus 10 a is also transmitted to the second switchableimaging apparatus 10 b, and vice versa, to provide audio communication.The teleconferencing application of FIG. 6D has an advantage overconventional teleconferencing systems in that the images captured of thepersons 13 a and 13 b are captured from a viewpoint central to thecorresponding display screen. Therefore, when each person is looking atthe image of the other person on the display screen of their respectiveswitchable imaging apparatus 10 a and 10 b, they will be lookingdirectly into the optical axis of the camera. As a result, the image ofthe first person 13 a will appear to be looking directly at the secondperson 13 b and vice versa. In prior art teleconferencing systems, theimage of the first person 13 a appears to be looking in a differentdirection since the camera captures the image of the first person 13 afrom a different direction than the display where the first person 13 ais looking (In conventional teleconferencing systems, the camera istypically positioned above the display.)

It should be noted that the switching behavior described with referenceto FIGS. 5A and 5B can be performed using a wide variety of patternssuitable for operation of the switchable imaging apparatus 10 in variousembodiments. In some cases, switching between the image display mode(FIG. 5A) and the image capture mode (FIG. 5B) can be initiated asneeded, such as by a user instruction, for example. In other cases, theswitching can be performed automatically, such as at a suitableswitching frequency (e.g., 60 Hz) that allows switching to beimperceptible to the human viewer, substantially avoiding perceptibleflicker in the displayed image. This can be useful for applications suchas displaying a preview image of the scene during an image compositionprocess, capturing a video sequence, using the imaging apparatus 10 toprovide a video teleconferencing function, or for use in conjunctionwith text display (e.g., for the teleprompter or karaoke applications).

FIGS. 7A and 7B illustrate an alternate embodiment of a switchableimaging apparatus 11 where the optical beam deflector 50 is positionedbetween the scene and the display screen 20 such that the imaging lightdoes not pass through the display screen 20 before being deflected bythe optical beam deflector 50. In this configuration, the positions ofthe optical beam deflector 50 and the display screen 20 are reversedrelative to the embodiment of FIGS. 5A and 5B. In this embodiment, anoptional protective layer 58 can be provided in front of the switchablebeam deflector 50 to protect the switchable beam deflector 50. Theprotective layer 58 can be a piece of transparent glass, for example.

When the switchable imaging apparatus 11 is controlled to operate in theimage display mode (FIG. 7A) the switchable beam deflector 50 is set tooperate in its non-deflecting state, so that it will be transparent andwill not cast a shadow in the displayed image, and the display screen 20is controlled to operate in its display state. In some embodiments,optional light blocking layer 36 can be used to block the light behindthe display so that the displayed image will only be viewable from thefront side. In other embodiments, the light blocking layer 36 can beexcluded or can be switched to a transparent state so that the displayedimage can be viewed from either the front or back side.

When the switchable imaging apparatus 11 is controlled to operate in theimage capture mode (FIG. 7B) the switchable beam deflector 50 is set tooperate in its deflecting state so that it will direct imaging lightfrom the scene onto the camera 34, and the display screen 20 iscontrolled to operate in an off state. Alternately, when operatingswitchable imaging apparatus 11 in the image capture mode, the displayscreen 20 can continue to display an image with the result being thatthe image will be partially blocked in the area of the liquid crystallayers in the switchable beam deflector 50 during the fraction of asecond required for the image to be captured. To compensate for thispartial blockage of the displayed image, the brightness of the displaypixels in the blocked area can be temporarily increased so that theimage appears to have uniform brightness when operated in an alternatingstate of image capture and image display, or embodiments where aswitchable light blocking layer 36 is used, it can be switched to atransparent state to provide a transparent view of the scene, or can beswitched to a light blocking or light scattering state according to thedesired behavior. For embodiments where it is not desired to support astate where the switchable imaging apparatus 11 appears to betransparent, one advantage of the FIG. 7A arrangement relative to theFIG. 5A arrangement is that the display screen 20 does not need to betransparent (or partially transparent) when it is not in its displaystate because the imaging light does not need to pass through it.

FIGS. 8A and 8B show an alternate embodiment of the invention in which aswitchable imaging apparatus 70 uses an array of switchable beamdeflectors 74. Each of the switchable beam deflectors 74 can use asimilar arrangement of liquid-crystal layers 54, such as those describedwith reference to FIGS. 2A and 2B. In the embodiment shown, eachswitchable beam deflector 74 extends across at least a portion of thesurface of imaging apparatus 70 in column-wise (or row-wise) fashion,and directs light from a section of the scene onto the camera 34. Eachof the switchable beam deflectors 74 can be individually switched totheir second deflecting state according to a sequential activationpattern to direct imaging light from the corresponding section of thescene onto the camera 34, thereby providing a set of partial images ofthe scene. The partial images can then be combined to form a completeimage of the scene. In some cases, the partial images may overlap andthe complete image can be formed by aligning the overlapping partialimages. Pixel values for the complete image can be determined byaveraging corresponding pixel values from the partial images in theoverlap regions. This configuration has the advantage that using aplurality of switchable beam deflectors 74 can provide an increasedfield of view relative to that which would be possible for a singleoptical beam deflector given a particular device geometry.

In one configuration, each optical beam deflector in the set of opticalbeam deflectors extends in a direction parallel to one edge of thedisplay screen 20, and is adapted to deflect light from a correspondingthin stripe of the scene into the camera 34. In this configuration, theimaging optics 32 can be a cylinder lens, and the imaging sensor 33 canbe a linear sensor array.

To capture an image, the controller 40 sequentially switches oneswitchable beam deflector 74 at a time into its deflecting state, whileswitching all of the other switchable beam deflectors 74 into theirnon-deflecting states. The controller 40 also sets the display 20 (or atleast a region of the display corresponding to the activated switchablebeam deflector 74) to operate in its transparent state. In this way, ascanned image can be obtained as a succession of linear images, obtainedone column (or row) at a time.

FIG. 9 illustrates the case where the k^(th) switchable beam deflector74 k is set to its deflecting state while the rest of the switchablebeam deflectors 74 are in their transparent non-deflecting states. Asshown in FIG. 9, the displayed image is partially interrupted or blockedby the k^(th) switchable beam deflector 74 k since it is in itsdeflecting state. The camera 34 in this embodiment is a linear devicethat can be one or more pixels wide by hundreds or thousands of pixelslong, energizable to capture and provide image data for each verticalcolumn (or horizontal row) of an image of the scene during the scansequence.

In one scanning embodiment using the arrangement of FIG. 9, controller40 (FIGS. 8A and 8B) synchronously switches a group of display pixels 26k including one or more adjacent columns (or rows) of pixels in thedisplay screen 20 to their transparent state at the same time that thecorresponding switchable beam deflector 74 k is in its deflecting state.The rest of the display pixels in the display screen 20 are set to theirdisplay state and can be used to display an image during the scansequence. By scanning in this way and obtaining one stripe of the imageat a time, the embodiment shown in FIGS. 8A, 8B and 9 enablessimultaneous display and image capture that, when performed at a highenough scanning frequency, can be essentially imperceptible to theviewing subject. That is, the viewing subject would see only the imagedisplayed on the display screen 20, unaware that the scanning sequencedescribed with reference to FIG. 9 was taking place.

Another embodiment of the invention is shown in FIG. 10 which comprisesa switchable imaging apparatus 30 that is capable of capturing imagesfrom two opposing sides simultaneously. The switchable imaging apparatus30 includes a transparent plate 110 incorporating two switchable beamdeflectors 50 a and 50 b, which are fabricated in opposing orientations.The two switchable beam deflectors 50 a and 50 b are used to provide twoindependently switchable optical systems. One optical system obtains animage along optical axis Oa, with light redirected onto optical axis Oa′by the switchable beam deflector 50 a, where the image is captured bycamera 34 a. The other optical system obtains an image along opticalaxis Ob, with light redirected onto optical axis Ob′ by a switchablebeam deflector 50 b, where the image is captured by camera 34 b. Thisexample shows two controllers 40 a and 40 b for controlling therespective switchable optical systems. However, it will be clear to oneskilled in the art that in other embodiments they can both be controlledby a single controller.

In an alternate embodiment, optical axis Ob′ is coincident with theoptical axis Oa′ so that imaging light from both a first scene in thedirection of the optical axis Oa and a second scene on the opposite sideof the transparent plate 110 in the direction of the optical axis Ob canbe redirected toward a single camera (e.g., camera 34 a). In thisconfiguration, an image of the first scene can be formed by controllingthe switchable beam deflectors 50 a to be in the deflecting state, andan image of the second scene can be formed by controlling the switchablebeam deflectors 50 b to be in the deflecting state.

Referring to FIG. 11, in some embodiments, the transparent plate 110 ofFIG. 10 can be sandwiched between two display screens 20 a and 20 b,wherein each of display screens 20 a and 20 b can be controlled toprovide a display state and a transparent state. An image can then bedisplayed on one or both of the display screens 20 a and 20 b when animage is not being captured by the respective switchable opticalsystems.

It will be recognized by one skilled in the art that the imagingapparatus configurations illustrated in FIGS. 10 and 11 which can beused to capture images in two different directions can be combined withthe configuration of FIGS. 8A-8 b which used a set of sequentiallyactivated switchable beam deflectors 74 to capture an image in a singledirection. In this case a plurality of beam deflectors can be arrangedto point in each of the two directions. An image of a first scene on afirst side of the imaging apparatus can be captured by sequentiallyactivating the beam deflectors oriented to deflect light from the firstside, and an image of a second scene on a second side of the imagingapparatus can be captured by sequentially activating the beam deflectorsoriented to deflect light from the second side.

The imaging apparatus configurations illustrated in FIGS. 10 and 11 canalso be combined with various other features that have been described inthe context of the other embodiments. For example, the light blockinglayer 36 of FIGS. 8A and 8B can be added on either side of thetransparent plate 110.

In the context of the present disclosure, the term “controller” is usedto encompass a broad range of possible devices that can execute storedinstructions and may include a dedicated logic processor ormicroprocessor or a more general purpose computer, such as a laptopcomputer or desktop workstation, for example. Controller 40 may alsohave a network connection to other processors or computers, wherein thenetwork connection is wired or wireless. Controller 40 may perform someof the functions needed for image acquisition and display, whilecommunicating with one or more other networked processors or computersfor performing additional operations, such as additional imageprocessing functions. The controller 40 will generally becommunicatively connected to a storage memory. The storage memory can beused for image storage and for storage of executable instructions forcausing the controller 40 controlling the operation of the switchableimaging apparatus.

In the context of the present disclosure, the term “memory” is used as ageneral term to encompass non-transitory tangible computer readablestorage medium of both non-volatile and volatile types. A processor caninclude or interact with one or more types of storage media, forexample; magnetic storage media such as magnetic disks (e.g., floppydisks or hard disks) or magnetic tape; optical storage media such asoptical disk, optical tape, or machine readable bar code; solid-stateelectronic storage devices such as random access memory (RAM), orread-only memory (ROM); or any other physical device or media employedas a program memory to store a program having instructions forcontrolling one or more computers or processors to practice the methodaccording to the present invention.

Example 1

In a first exemplary embodiment, a switchable beam deflector 50 as shownin FIGS. 2A and 2B has two liquid crystal layers 54 made using liquidcrystal material E63 from Merck. This liquid crystal material isswitchable between refractive indices of n_(L,e)=1.74 and n_(L,o)=1.52in response to an applied voltage signal. If the substrate 52 isfabricated with a material having a refractive index of n_(S)=1.74, thisprovides a critical angle θO_(c)=60.9° when the refractive index of theliquid crystal material is at its lower value. The liquid crystal layersare positioned as shown in FIGS. 2A and 2B, with the layer nearer to thecamera being oriented at an angle of θ_(L2)=22.5°, and the layer furtherfrom the camera being oriented at an angle of θ_(L1)=66.5°. With thisarrangement, the light rays form consistent angles with the liquidcrystal layers. The angle formed by the light rays and the normal to thesurfaces of the liquid crystal layers of 67.5° is well above thecritical angle θ_(c)=60.9° for TIR behavior. The thickness of the liquidcrystal layer should be larger than the penetration of an evanescentwave. For example, a thickness of 2-7 μm is commonly used in liquidcrystal displays, and would work well for the liquid crystal layers 54in the switchable beam deflector 50.

Example 2

Similar to Example 1, using a liquid crystal material 18349 from Merck,which has refractive indices of n_(L,e)=1.80 and n_(L,o)=1.50. Assumingthat the substrate 52 is fabricated with a material having a refractiveindex of n_(S)=1.50, the critical angle θ_(c)=57.6, which is well belowthe angle formed by the light rays and the normal to the surfaces of theliquid crystal layers. Again, TIR conditions are provided.

Example 3

A transparent plate 110 similar to that shown in FIGS. 3A and 3B wasdesigned. In this design, the transparent plate 110 was 50 mm high(top-to-bottom dimension in FIG. 3A) and 10 mm thick (left-to-rightdimension in FIG. 3A), and was made from an optical material with arefractive index of 1.53. If the switchable imaging apparatus 120 has a16:9 format, the width of the transparent plate 110 (out-of-pagedimension in FIG. 3A) would be 89 mm. This would correspond to a 50mm×90 mm display with a diagonal dimension of approximately 4 inches,which is comparable to display sizes used for consumer digital cameras.The optical path between the bottom edge of the transparent plate wherethe camera is located and the center of the switchable beam deflector 50is then 25 mm. The switchable beam deflector aperture provided by theliquid crystal layer that is closer to the camera is then effectively 5mm in the thickness direction and the full width of the switchable beamdeflector in the other direction.

For this example, a 16:9 format image was to be captured so the camera34 was oriented with the narrow dimension of the imaging sensor 33aligned to the 5 mm aperture. For an imaging sensor 33 with a 7.2 mmdiagonal ( 1/2.5″ format) and a 3.45 mm narrow dimension, consideringthe refraction effect provided by the transparent plate 110, the fieldof view as limited by the aperture of the switchable beam deflector 50is then 17.5° in the narrow dimension and 36.5° in the diagonaldimension. This field of view corresponds to a 35 mm equivalent focallength of 65.7 mm which is between a wide angle and a telephotoarrangement. In addition, if the 17.5° field of view is imposed on topof the 66.5° incident angle provided in Example 1, the steepest incidentangle in the field of view is then 66.5°−17.5°/2=57.75° which is abovethe critical angle of Example 2.

Example 4

To further reduce the angle of incidence of the rays onto the liquidcrystal layers, three liquid crystal layers can be provided rather thanthe two liquid crystal layer arrangement shown in FIG. 3A. This reducesthe angle of incidence to 15° and the effective aperture provided by theswitchable beam deflector is then ⅓ of the thickness of the transparentplate. The field of view associated with this arrangement is now 11.5°.

Example 5

The design of Example 4 was further improved by having two adjacentswitchable beam deflectors with slightly different angles of the liquidcrystal layers so that adjacent fields of view are provided. In thisway, images can be captured in sequential pairs and stitched together toform stitched images with substantially twice the field of view.

Referring to FIG. 12, according to one embodiment of the presentinvention, a switchable image capture apparatus 80 having a transparentviewfinder mode is provided. Photographer 12 views subject 16 throughimage capture apparatus 80, which appears to be a transparent sheet ofglass, within a frame 84. This helps to provide a more natural imagecapture session. Subject 16, in turn, may see photographer 12 throughthe image capture apparatus 80, as was described in FIG. 6C. Inalternate embodiments, the subject 16 may see a blank screen or otherimage content displayed on display screen 20, depending on the setup ofimage capture apparatus 80. One or more user controls 88, are providedto enable the photographer to perform appropriate tasks. In someembodiments, the display screen 20 can be a touch sensitive surface sothat the user controls 88 can be provided using touch-sensitiveon-screen symbols that the photographer 12 can touch. In otherembodiments, the user controls 88 can be positioned on the frame 84. Theuser controls 88 can include an image capture control that can beactivate in order to capture an image 82. The user controls 88 can alsoinclude controls for performing zoom or focus adjustment, or to adjustvarious camera settings.

In one embodiment of the present invention, the image capture apparatus80 behavior uses the following sequence:

-   -   (i) transparent viewfinder mode for capturing images (in this        mode the switchable beam deflector 50 is in its non-deflecting        state, and the display screen 20 is in its transparent state);    -   (ii) image capture mode initiated by activation of user control        88 (in this mode the switchable beam deflector 50 is in its        deflecting state, and the display screen 20 is in its        transparent state);    -   (iii) image display mode for displaying the captured image,        either for a predetermined time period or until instructed        otherwise by the viewer (in this mode the switchable beam        deflector 50 is in its non-deflecting state, and the display        screen 20 is in its display state); and    -   (iv) return to transparent viewfinder mode (i).

According to an alternate embodiment of the present invention, there isprovided a transparent image capture apparatus 80 that employsswitchable imaging apparatus 120 described with reference to FIG. 3B,which does not include display screen 20.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

PARTS LIST

-   10, 10 a, 10 b switchable imaging apparatus-   11 switchable imaging apparatus-   12 photographer-   13 a, 13 b person-   14, 14 a, 14 b image-   15 communications network-   16 subject-   17 photographer's view-   18 field of view-   19 subject's view-   20, 20 a, 20 b display screen-   26 k group of display pixels-   30 switchable imaging apparatus-   32 imaging optics-   33 imaging sensor-   34, 34 a, 34 b camera-   36 light blocking layer-   40, 40 a, 40 b controller-   44 control wires-   50, 50 a, 50 b switchable beam deflector-   52 substrate-   54 liquid crystal layer-   56 air gap-   58 protective layer-   60 first material-   62 second material-   64 interface-   70 switchable imaging apparatus-   74, 74 k switchable beam deflector-   80 switchable image capture apparatus-   82 image-   84 frame-   88 user control-   110 transparent plate-   111 a, 111 b, 111 c transparent plate sections-   113 a, 113 b transparent electrodes-   120 switchable imaging apparatus-   O, Oa, Ob optical axis-   O′, Oa′, Ob′ redirected optical axis-   R1, R2 ray

1. A switchable imaging apparatus having a transparent viewing mode forviewing a scene and an image capture mode for capturing an image of thescene, comprising: a transparent plate having a front surface, whereinthe scene is viewable through the transparent plate when the imagingapparatus is in the transparent viewing mode; an optical beam deflectorpositioned within the transparent plate, or in proximity to thetransparent plate, wherein the optical beam deflector is switchablebetween a first non-deflecting state and a second deflecting state, suchthat when the optical beam deflector is in the first non-deflectingstate, light from the scene passes through the optical beam deflector inan undeflected direction, and when the optical beam deflector is in thesecond deflecting state, light from the scene is deflected from a firstoptical axis perpendicular to the front surface of the transparent plateonto a second optical axis parallel to the front surface of thetransparent plate; a camera positioned along the second optical axis ina location peripheral to the transparent plate; and a controller whichsynchronously switches the optical beam deflector between the firstnon-deflecting state and the second deflecting state and initiatescapture of an image by the camera, thereby providing the transparentviewing mode and the image capture mode.
 2. The switchable imagingapparatus of claim 1 wherein the controller switches the optical beamdeflector to the first non-deflecting state to provide the transparentviewing mode.
 3. The switchable imaging apparatus of claim 1 wherein thecontroller switches the optical beam deflector to the second deflectingstate and initiates capture of an image by the camera to provide theimage capture mode.
 4. The switchable imaging apparatus of claim 1wherein the optical beam deflector includes at least one liquid crystalplane positioned at an oblique angle relative to the first optical axis,the liquid crystal plane being switchable between a first refractiveindex and a second refractive index, wherein when the liquid crystalplane has the first refractive index light from the scene is transmittedundeflected, and when the liquid crystal plane has the second refractiveindex light from the scene is deflected by total internal reflection. 5.The switchable imaging apparatus of claim 1 wherein the camera includesan imaging lens positioned along the second optical axis for focusingthe imaging light onto an imaging sensor.
 6. The switchable imagingapparatus of claim 5 wherein the imaging sensor includes aone-dimensional array of sensor pixels.
 7. The switchable imagingapparatus of claim 5 wherein the imaging sensor includes atwo-dimensional array of sensor pixels.
 8. The switchable imagingapparatus of claim 1 wherein the transparent viewing mode is used toprovide a transparent viewfinder for composing an image of the scene. 9.The switchable imaging apparatus of claim 1 wherein the controlleralternates between the transparent viewing mode and the image capturemode according to a switching frequency to capture a sequence of images.